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  • Lorianna Kastrop

Accessory Dwelling Units: Why you may need a property survey

Many homeowners are considering adding an accessory dwelling unit to their property. ADU’s, (also known as Secondary Dwelling Units, grandmother cottages, in-law units, etc.) have become popular due to a new CA state law that relaxes some of the building code regulations. With California housing needs and rents skyrocketing, ADU’s can provide options for renters, and income for homeowners.

Often, the City or County jurisdiction will require a property survey in order to get a building permit for an ADU. Why do you need a survey? What triggers the survey requirement? This article will address some of the issues around the increased need for property surveys.

The underlying reason that Cities and Counties are now being so strict about property lines is that the trend is to build the maximum amount of square footage possible on the property. Construction will occur at or near the allowed setbacks from the property line. Proper verification of the property lines in advance avoids future litigation for buildings constructed in areas that have encroached illegally into the setback areas. Property owners build fences or install landscaping on what they believe to be the property line, but over time fences and trees may have encroached on neighboring property due to mistakes in fence construction and repairs, erosion or ground settlement, and tree roots.

Here are some of the triggers that will cause the City or County to require a survey of the property before granting a building permit:

  1. You want to maximize the amount of square footage and may be close to side and rear yard setbacks. The interpretation of what is “close” is up to your local jurisdiction.

  2. Requirement to verify property lines. (Note: The existence of a fence does not necessarily prove where the property line is located.) If the property has never been surveyed before, the City or County may want proof that the setbacks are verified.

  3. A survey will allow calculations of the pervious area. Pervious areas allow water drainage into the soil or ground cover. Impervious areas are typically paved—patios, driveways, building foundations, etc. Most cities and counties have a limit on the percentage of impervious area on a property. Additional construction (of the ADU) increases your impervious area percentage. An accurate calculation can help determine the allowable square footage of the ADU.

  4. Property lines that are unclear due to an odd-shaped lot, a curved street, or a steep slope will often trigger a survey requirement.

If you know your property has been surveyed already (such as for a previous project), it will be worth your time to find that paperwork in your records or re-contact the surveyor for a copy. If not, then getting a survey might be the first step for your ADU project. Because of the amount of building going on in the Bay Area, surveyors are currently swamped with work. Getting an appointment for a survey as soon as possible will help your project move more quickly through the design and permitting process.

Architects do not typically provide surveying services but can refer you to surveyors that they have successfully worked with in the past. If you are planning to build an ADU on your property, or any other new construction, ask your architect whether he/she knows if your jurisdiction typically requires a survey. If so, then that will be one of the first steps for your project and should be started without delay. Thanks for reading, and as always, we are Designing for Your Reality.

Lorianna Kastrop, Vice President, The Kastrop Group, Inc. Architects

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